1. Technical Field
Embodiments of the present invention relate to a heat exchanger and a gas-fired furnace comprising the heat exchanger.
2. Description of the Related Art
A forced hot air, gas-fired furnace in the related art generally comprises a burner, a heat exchanger, a secondary coil, a flue gas inducer and an air ventilation fan.
The heat exchangers in hot air, gas-fired furnaces may typically be categorized into two types: one type is known as tubular type heat exchanger and the other as clamshell type heat exchanger. The tubular type heat exchanger is fabricated by bending an aluminized steel tube into a serpentine shape having a plurality of straight segments and curved segments and then fixing parallelly a plurality of serpentine tubes on endplates. For the tubular type heat exchanger, due to the needs to satisfy the gas combustion space and heat transfer surface area requirements, the tube diameter is generally configured to be sufficiently large. Furthermore, for the portion of tube bend, tube metal experiences lattice stretching at the outer bend surface and a compression at the inner bend portion. The bend radius must be large enough to avoid excessively stretching or compressing the tube metal. Therefore, it is difficult to achieve the compactness of a tubular heat exchanger design in order to reduce the height of the gas-fired furnace, resulting in poor cost-effectiveness in shipping the gas-fired furnace and installation of the gas-fired furnace. The clamshell type heat exchanger is fabricated by connecting a plurality of clamshells side by side to the heat exchanger endplates. Two mating clamshells define a flue gas passage, which requires a long design cycle to achieve the optimized clamshell surfaces in terms of effective heat transfer, thermal stress management, and manufacturability. The costs associated with tooling and manufacturing equipment are high.